The present invention relates to a bearing submerged for use in molten metal and a continuous hot-dip plating apparatus using the bearing.
Hitherto, sliding bearings are used as molten metal immersion bearings for a continuous hot-dip plating apparatus, etc. because of the simplicity of their construction and convenience of their installation thereof. However, in these conventional bearings, metal compound fine particles which are called dross and oxide fine particles (those fine particles are referred to as solid particles hereunder) easily to penetrate between a shaft and a bearing during its rotation, and serve as abrasive grains to violently wear the bearing sliding members. Further, biting of solid particles raises frictional resistance, whereby smooth rotation is prevented.
In order to prevent the penetration of the solid particles between the sliding surfaces, a bearing having a construction covering the entire periphery of the shaft with carbon material is proposed in JP A 5-70915 (1993). However, with only the construction that the bearing covers all the periphery of the shaft, once solid particles penetrate between the sliding surfaces of the shaft and the bearing, and once the sliding surface of the shaft or the bearing are worn, a gap between the sliding surfaces of the shaft and the bearing increases and the solid particles easily penetrate further, as a result, the wear increases with increasing speed. Further, in order to prevent the penetration of the solid particles when the bearing covers the entire periphery of the shaft, it is necessary to control precisely the gap. However, since in practice changes in dimension or deviation in axes occur due to thermal expansion of the bearing submerged in molten metal, it is impossible to control precisely the gap.
Further, JP A 3-177552 (1991) discloses a method in which pins are set up on the sliding surface of a bearing or a plate is arranged to provide a convex shape on the sliding surface of the bearing, and solid particles penetrated between the sliding surfaces of the shaft and the bearing are scraped off thereby. However, this method does not solve the problem of solid material penetration because frictional resistance becomes large, solid particles become easy to penetrate from the concave shape on the sliding surface, etc.
Further, when molten metal immersion bearings of conventional construction are used for a continuous hot-dip plating apparatus, since play occurs due to wear of bearing portions and the quality of products is detracted, nowadays it is necessary to exchange the bearings frequently.